The present invention relates to a new adhesive lacquer, a process for joining a thermoplastic resin to a thermosetting resin by means of this lacquer as well as the products obtained at the various stages of this process.
It has already been proposed to combine the properties of thermoplastic resins such as, for example, polyvinyl chloride, polystyrene and acrylonitrile-butadiene-styrene resins with those of thermosetting resins such as, for example, polyester resins, by producing structures in which these two types of material are joined by gluing.
However, it has not been possible hitherto to produce this combination satisfactorily because the various methods proposed for producing adhesion do not succeed in imparting sufficient resistance to delamination to this combination.
Thus, for example, it has been proposed, in British Pat. No. 866,776 in the name of ARTRITE RESINS Ltd. of Mar. 12th, 1957 to produce containers made of polyvinyl chloride equipped with an outer layer of reinforced polyester resin containing a crosslinking monomer (acrylate ester) which exerts a dissolving effect on polyvinyl chloride. This process in fact leads to an excellent result when the layer of polyester resin, as is claimed, is placed outside the container. It has been found, however, that if the polyester resin is placed inside the container, the adhesion between the layer of thermosetting resin and the wall of polyvinyl chloride becomes very uncertain.
This defective result can be explained by the fact that, during their crosslinking, polyester resins undergo shrinkage. Consequently, this phenomenon leads to adhesion of a mechanical nature between the two layers of resin when the layer of polyester resin is placed outside the reinforced article while it promotes delamination when, on the other hand, the layer of polyester resin is placed inside the article.
According to German Pat. application No. 1,958,647 in the name of KARLSKRONA-VARVET A. B. of Nov. 22nd, 1969, adhesion of a sheet of plastic such as polyvinyl chloride to a layer of thermosetting resin is achieved by using, as the adhesive, a solution of polymethyl methacrylate in methylene chloride. However, the laminates produced according to this process have insufficient resistance to delamination to enable them to be used in practice.
Accordingly, there has been a continuing search for an adhesive that can join a thermoplastic resin with a thermosetting resin to produce an article that has good resistance to delamination.